RLEp

The RLEp format is a variant of the RLE compression (Run-length encoding) with the particularity of having 2 bits reserved to encode a pattern type and 6 bits for its length (max length is 64 bytes per pattern).

Pattern types:

Val	Name	Min len	Desc.
[00¦len]	Default value	2	Repeat default value len times. The default value is either 0 or the first byte of the RLEp code.
[01¦len][value]	1 byte	2	Repeat the next character len times.
[10¦len][value][value]	2 bytes	2	Repeat the next two characters len times.
[11¦len][value][value]...	Uncompress	0	Followed by a list of non-compressed bytes of size len.

The efficiency of RLEp encoding is highly data-dependent. Data with "holes" or repetitions, such as sprites, can have a very good compression ratio, whereas a bitmap image teeming with detail will have a very poor (or even negative) compression ratio.